In Sausalito, visitors trek from the Sierra to the Golden Gate in minutes

A group of about 30 men, women and children trekked from the Sierra Nevada Mountains through the Sacramento River Delta and out into San Francisco Bay on Saturday, ending at the Golden Gate Bridge. They did it in less than 90 minutes.

They were all visiting the Bay Model in Sausalito, where time and distance are a little shorter than they are in the real world. In this scaled down simulacrum of the bay and beyond, the 24-hour cycle of tides occurs every 14.9 minutes, with Marin County tap water streaming in and out of the Golden Gate. You can travel from the mountains to the sea by walking up a ramp, meandering through a hallway with murals of the delta on the walls and then breaking out into the expanse of San Francisco's three interconnected bays, all spread out in a gigantic scale model the size of two football fields.

"There's nothing like a three-dimensional model to really make sense of things," said Christine Arman of Los Gatos, who was visiting the model with her husband, Mark, and their two children, Geneva, 2, and 12-year-old Charlie. "I'm a Bay Area native. I grew up on the Peninsula. But I still didn't fathom the size of the bay and the wetlands around it. It's interesting to see how big it really is."

The Armans were along on the free "Trekking the Model" tour, a monthly event led on Saturday by Army Corps of Engineers Senior Ranger Bill Cope, whom everyone calls "Ranger Bill."

"The Bay Model probably saved San Francisco Bay," he told the tour group, explaining how it was originally built in 1957 to test a radical plan by theater producer John Reber to build dams at the mouth of the Sacramento River that would feed two freshwater lakes within the bay, supplying drinking water for the Bay Area.

"Fortunately," Cope said, "it failed."

Constructed inside a former parts warehouse for Marinship, the famed Sausalito shipyard that built Liberty Ships during World War II, the Bay Model was a scientific research facility until January of 2000, when computer technology made it obsolete.

"Then it's mission changed to education and culture," Cope explained, noting that up to 160,000 people a year visit the Bay Model from all over the world, including China, the Netherlands and Japan.

"They come here just to see this historic model, the only operational hydraulic working model in all of America, perhaps the entire western hemisphere," he said.

Operated by the Corps of Engineers, the facility also features a number of fascinating side exhibits, including a popular diorama that uses colored white and blue lights to show how the snow pack melts in the Sierra, sending water down through the delta and out into the bay. In this drought year, the diorama takes on added impact.

"It really makes you want to go home and conserve water," said Reta McEwen, who was visiting from Stanislaus County with her husband, Mark, and college student daughter, Mary, 22, who took the day off from classes at UC Santa Cruz to see the Bay Model, a trip she's wanted to take with her parents for three years.

"It's really cool," she said, heading off to take a second look at things she may have missed on the tour. The model may be a scaled down version of the real thing, but it is in no way a miniature. Asked what surprised her most about it, she said,